1. Field of the Invention
This invention relates to air pressure sensors and is particularly although not exclusively applicable to air pressure sensors for use in batch counting apparatus such as apparatus for counting signatures delivered in a "shingled" stream from a printing machine to a batching machine to form the required batches of signatures for subsequent binding.
2. Description of the Prior Art
Various mechanical devices are available for counting stacks of sheets but none is suitable for counting a "shingled" stream of sheets or collections of sheets in signature form.